The present invention relates to cutlery and, more particularly to scissors or shears having toothed or serrated blades, such as pinking shears, and means for adjusting the tip pressure of the blades.
Heretofore, one of the difficulties associated with conventional pinking scissors or shears is the inability of the prior art shear constructions to achieve a smooth cutting action along the entire length of the blades when different materials of varying thickness are cut. This is especially so at the tips or free ends of the blades farthest from the pivot point of the blades. Shears which lack the capability of achieving a quick and conventional adjustment of blade tip pressure are not practical for use in cutting differing fabric materials of widely varying thickness as is typical, for instance, in the garment making arts.
A further limitation of conventional pinking shears which are not provided with a blade tip pressure adjustment mechanism is the blade wear which occurs after a period of use and which can render the shears virtually useless for cutting materials of any thickness.
Several devices are known in the prior art for making adjustments between pinking shear blades. One such device is disclosed in U.S. Pat. No. 3,170,237 to Weidauer. This patent discloses that the pressure between the cutting blades may be adjusted by varying the force applied to a pair of dish-shaped spring washers arranged on the pivot bolt of the blades. The adjustment is accomplished by tightening the pivot nut secured to the pivot bolt. An anti-friction ball thrust bearing is provided between the blades to reduce the friction therebetween.
Another prior art device which is utilized to adjust the alignment of pinking shear blades to provide a workable relationship therebetween is disclosed in U.S. Pat. No. 2,000,852 to Langbein. The adjustment mechanism of this prior art device comprises a plurality of balls mounted between the blades on a V-shaped raised portion arranged concentrically about the pivot bolt. The balls act as a ball bearing to reduce friction between the blades and each ball is individualy adjustable by means of a screw to maintain the blades in alignment.
The prior art pinking shears disclosed in the aforesaid patents are of comparatively complex and expensive construction and require the use of an anti-friction bearing arrangement about the pivot bolt for reducing the friction between the blades.